PLSY (NEED TO CONTROL PULSES)

[marcadams]

I'm trying to install a new Cognex checker camera that relies on pulses to do a job change. Example: 5 pulses with call up job 5, 3 pulses will call up job 3 and so on.... I have a Q-Series and need to make that happen. I have tried using the PLSY statement but it's not doing what I want it to. Am I using the wrong statement or is there a better way to control the amount of pulses for this case? I've attached the documentation I'm working with. Any help would be a appreciated.

[Sergei Troizky]

Being properly programmed, PLSY should work, however you do not need high-speed output for this application. There are no limitations on the slower side. Use regular output and generate the necessary number of pulses programmatically. Edited December 8, 2013 by Sergei Troizky

[marcadams]

Can you give me an example. I'm somewhat a novice. Thanks.

[panic mode]

assuming scan time is >=1ms something like this shouldwork. note, this is an example, it is your job to make it work. explanation: X0,X1,X2 are used as job trigger commands. each sets desired number of pulses into D0. if value of D0 is greater than zero, we need to change job (Y6). while change job is active, we pulse job select (Y5). of course, on each pulse we decrement D0 so when D0 is zero/empty, Y6 and Y5 turn off. timing diagram in your picture shows that 'job change' is high BEFORE first 'job select' pulse. to ensure that, rung with Y6 is after Y5 (this way Y6 is on for one scan before Y5). there seem to be same condition on the trailing side but i don't think that is an issue but if it is, it is easy to fix. if the program is small and scan time is <1ms, there need to be time delay to shape Y5.

[Sergei Troizky]

Here it is for FX series, but should not differ for Q.

[plcdp]

I am doing this with an FX series, and it works fine. The job change input on the Cognex needs to be at a frequency of no more than 500 htz. Also the pulse width needs to be at least 1ms., on and off. The example Sergei provided would not work if your scan time is less than 1 ms. Just something to keep in mind. Hope this helps, Dave

[marcadams]

Thanks to you all. This will help!

[ianreeves]

Hi we use quite a few checkers. One thing that can confuse you is these cameras are very sensitive to contact bounce. So always use a transistor output or a RC "damper" on the output.